1. Field of the Invention
The present invention relates to, in an image recording apparatus by which an image is recorded on a recording material based on print data transferred at a predetermined transfer rate, a method of conveying a recording material in which the recording material is conveyed to an image recording stage, and a device for controlling conveying of the recording material.
2. Description of the Related Art
A technique has been developed, wherein a printing plate (hereinafter referred to as a photopolymer plate) having a photosensitive layer (for example, a photopolymerization layer) provided on a support is used and an image is directly recorded on the photopolymerization layer of the photopolymer plate by a laser beam or the like (an automatic exposure apparatus for printing plates).
In such a technique, recording of an image on a photopolymer plate is rapidly carried out, and therefore, photopolymer plates need to be successively fed into an exposure section. Therefore, preferably, a plurality of photopolymer plates are in advance placed on standby at a predetermined position in a state of being stacked, and automatically taken out one-by-one and sent to an exposure stage of an exposure section. Further, it is preferable that the photopolymer plate sent thereto is conveyed along a predetermined proper conveying path.
The photopolymer plate is adapted to be wound around a print drum at the time of printing. In order that the photopolymer plate be positioned at this time, a process of forming a punch hole is provided in the automatic exposure apparatus for printing plates. The punch-hole forming process is carried out on a surface table which serves to effect sub-scan movement and is a base at the time of exposure for the photopolymer plate. The punch hole becomes a reference when an exposure is performed.
For this reason, the photopolymer plate transferred to the surface table is required so as to be positioned at a regular position.
Even if transfer of print data is stopped and exposure in the exposure section is cancelled, the printing plate with the punch holes formed thereon cannot be reused and is therefore discarded. On the other hand, in the case of a printing plate with no punch hole formed thereon, when transfer of print data is stopped and exposure in the exposure section is cancelled, the printing plate is discharged as is and can be reused, which results from that it suffers no change, namely, no punch hole formed thereon.
That is, handling of the printing plate after exposure processing has been cancelled based on stoppage of print-data transfer, varies depending on a state in which the operation of forming the punch hole is performed or not. Accordingly, preferably, cancellation of exposure processing is determined before the punch-hole forming operation is performed.
However, conveying of the printing plate, which is started in parallel with start of print-data transfer, is irrespective of transfer state of print data after start of print-data transfer, and in most cases, the printing paper arrives at the exposure stage in the first half period of the print-data transfer, and a probability at which the printing plate is saved due to stoppage (cancellation) of exposure, becomes low. As a result, there exists a drawback in that an amount of printing plates to be discarded, having punch holes formed thereon, increases.
For reference, the print data is adapted to be transferred from a terminal equipment such as an external personal computer, and an amount of the data is widely set in the range from 100 MB to 1 GB (“B” is an abbreviation for byte). Further, the transfer rate is set at 7 Mb/sec or thereabouts. Accordingly, the time required for transferring the minimum amount of data is about 14.3 seconds, and the time required for transferring the maximum amount of data is about 143 seconds. On the other hand, the time when the printing paper is conveyed from a conveying start position to a position in the punch hole forming process is about 15 seconds, and the time when the printing paper is conveyed to the exposure stage is about 30 seconds.
In view of such circumstances as described above, when exposure processing is cancelled, most of printing papers are practically wasted.